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If supply frequency of induction motor increase, speed will
Remain same
Increase
Decrease
Zero
Increase
The synchronous speed of an induction motor is directly proportional to the supply frequency. Therefore, increasing the frequency results in a proportional increase in the magnetic field's rotational speed, which in turn increases the motor's operating speed.
The synchronous speed of an induction motor is directly proportional to the supply frequency. Therefore, increasing the frequency results in a proportional increase in the magnetic field's rotational speed, which in turn increases the motor's operating speed.
NsтАЛ=P120fтАЛ тАФ Synchronous speed formula where f is frequency and P is poles
NrтАЛ=NsтАЛ(1тИТs) тАФ Rotor speed formula where s is slip
The stator of an induction motor creates a rotating magnetic field (RMF) that rotates at the synchronous speed, defined as NsтАЛ=P120fтАЛ. Since the rotor speed NrтАЛ is determined by NrтАЛ=NsтАЛ(1тИТs), any increase in frequency (f) leads to an increase in NsтАЛ, which directly forces the rotor speed to rise assuming the slip (s) remains relatively constant under given load conditions.
Synchronous speed is directly proportional to frequency.
Higher frequency leads to higher speed at a constant number of poles.
V/f ratio is usually kept constant to maintain flux and torque capability when changing frequency.
The rotor follows the RMF, hence its speed tracks the synchronous speed.
Wide range of speed control by varying frequency
Improved energy efficiency in variable speed applications
Potential for motor overheating if V/f is not maintained
Requires complex power electronic drives (VFD)
Variable Frequency Drives (VFD)
Industrial fan and pump speed control
Conveyor belt systems
Increasing frequency beyond the rated value can lead to reduced torque capability due to the constant voltage constraint (field weakening region).
Option A is incorrect because speed depends on frequency. Option C is incorrect as frequency is in the numerator of the NsтАЛ equation.
B is correct тАФ The synchronous speed of an induction motor is directly proportional to the supply frequency (NsтАЛтИЭf), so increasing frequency increases the speed.
Always remember the relation NsтАЛ=P120fтАЛ; this is the most fundamental equation for analyzing any AC machine's speed behavior in competitive exams.